Clutch device

ABSTRACT

A prime mover includes a stator fixed to a housing, and a rotor rotatable relative to the stator. The prime mover is capable of outputting torque from the rotor by being supplied with electric power. A speed reducer is capable of reducing the torque of the prime mover and outputting the reduced torque. The speed reducer includes a sun gear rotatable integrally with the rotor, and planetary gears capable of revolving in a circumferential direction of the sun gear while rotating in a state of meshing with the sun gear. A gear width of the sun gear is set such that a length in the axial direction by which the sun gear and the planetary gear are overlapped is smaller than a gear width of the planetary gear.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of InternationalPatent Application No. PCT/JP2020/028600 filed on Jul. 23, 2020, whichdesignated the U.S. and claims the benefit of priority from JapanesePatent Application No. 2019-138331 filed on Jul. 26, 2019, and JapanesePatent Application No. 2020-125633 filed on Jul. 22, 2020. The entiredisclosures of all of the above applications are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to a clutch device.

BACKGROUND

Conventionally, there is known a clutch device that allows or interruptstransmission of torque between a first transmission portion and a secondtransmission portion by changing a state of a clutch to an engaged stateor a disengaged state.

SUMMARY

A clutch device according to at least one embodiment includes a housing,a prime mover, a speed reducer, a rotational translation unit, a clutch,and a state changing unit. The prime mover includes a stator fixed tothe housing, and a rotor rotatable relative to the stator. The primemover outputs torque from the rotor by supply of electric power to theprime mover.

The speed reducer reduces torque of the prime mover and outputs thereduced torque. The rotational translation unit includes a rotationportion that rotates relative to the housing upon receiving an input ofthe torque output from the speed reducer, and a translation portion thatmoves relative to the housing in an axial direction in accordance withrotation of the rotation portion relative to the housing.

The clutch is provided between a first transmission portion and a secondtransmission portion that are rotatable relative to the housing. Theclutch allows transmission of torque between the first transmissionportion and the second transmission portion in an engaged state of theclutch, and interrupts the transmission of torque between the firsttransmission portion and the second transmission portion in a disengagedstate of the clutch. The state changing unit receives a force along theaxial direction from the translation portion and changes a state of theclutch to the engaged state or the disengaged state according to aposition of the translation portion in the axial direction relative tothe housing.

The speed reducer includes a sun gear rotatable integrally with therotor, and a planetary gear configured to revolve in a circumferentialdirection of the sun gear while rotating in a state of meshing with thesun gear.

A gear width of the sun gear is set such that a meshing length betweenthe sun gear and the planetary gear is smaller than a gear width of theplanetary gear.

BRIEF DESCRIPTION OF DRAWINGS

The details of one or more embodiments are set forth in the accompanyingdrawings and the description below. Other features and advantages willbe apparent from the description and drawings, and from the claims. Inthe drawings:

FIG. 1 is a cross-sectional view showing a clutch device according to afirst embodiment:

FIG. 2 is a cross-sectional view showing a part of the clutch deviceaccording to the first embodiment;

FIG. 3 is a schematic diagram of a 2kh-type strange planetary gear speedreducer, and a table showing a relationship among an input and outputpattern, an inertia moment, and a speed reduction ratio;

FIG. 4 is a schematic diagram of a 3k-type strange planetary gear speedreducer, and a table showing a relationship among an input and outputpattern, an inertia moment, and a speed reduction ratio:

FIG. 5 is a diagram showing a relationship between a stroke of atranslation portion and a load acting on a clutch;

FIG. 6 is a cross-sectional view showing a sun gear and a vicinitythereof in the clutch device according to the first embodiment;

FIG. 7 is a diagram of the planetary gear of the clutch device accordingto the first embodiment as viewed in an axial direction;

FIG. 8 is a cross-sectional view taken along a line VIII-VIII in FIG. 7;

FIG. 9 is a perspective view showing a carrier and the planetary gearsof the clutch device according to the first embodiment;

FIG. 10 is a cross-sectional view taken along a line X-X in FIG. 7;

FIG. 11 is a diagram showing a relationship between a meshing lengthbetween the sun gear and the planetary gear and a remaining gap betweena tooth portion of the sun gear and a tooth portion of the planetarygear;

FIG. 12 is a cross-sectional view showing a clutch device according to asecond embodiment;

FIG. 13 is a cross-sectional view showing a sun gear and a vicinitythereof in a clutch device according to a third embodiment;

FIG. 14 is a cross-sectional view showing a part of a clutch deviceaccording to a fourth embodiment; and

FIG. 15 is a cross-sectional view showing a part of a clutch deviceaccording to a fifth embodiment.

DETAILED DESCRIPTION

To begin with, examples of relevant techniques will be described.

A clutch device according to a comparative example includes a speedreducer that reduces torque of a prime mover, and the speed reducerincludes a sun gear, planetary gears, and two ring gears. Each of thetwo ring gears has internal teeth capable of meshing with the planetarygears each of which is capable of revolving while rotating in a state ofmeshing with the sun gear. One of the two ring gears is fixed to ahousing that accommodates the speed reducer. The other of the two ringgears is provided so as to be integrally rotatable with a drive camprovided in a ball cam.

The numbers of internal teeth of the two ring gears are set to bedifferent from each other. Accordingly, when the sun gear is rotated bythe torque of the prime mover, the drive cam rotates relative to thehousing, and a driven cam moves relative to the housing in the axialdirection. As a result, the state of the clutch is changed to an engagedstate or a disengaged state, and transmission of torque between a firsttransmission portion and a second transmission portion is allowed orinterrupted.

In the clutch device of the comparative example, since it is necessaryto arrange the two ring gears in series in the axial direction, a gearwidth, which is a length of the gears in the axial direction of theplanetary gear, inevitably increases. In the clutch device, in order torestrict movement in the axial direction of a carrier that keeps arelative position between the multiple planetary gears, the sun gearprotrudes from an end surface of the carrier, and a retaining ring isprovided. Therefore, a gear width of the sun gear also increases withthe protrusion.

In the speed reducer configured as described above, at the time of theplanetary gear tilting with respect to the sun gear, a clearance thathas been formed is reduced by a degree proportional to a meshing widthand a tilting angle between the sun gear and the planetary gear. Whenthe clearance becomes zero, a so-called double-tooth meshing phenomenonoccurs between the sun gear and the planetary gears, and thus the speedreducer may not normally operate.

In contrast, a clutch device according to the present disclosureincludes a housing, a prime mover, a speed reducer, a rotationaltranslation unit, a clutch, and a state changing unit. The prime moverincludes a stator fixed to the housing, and a rotor rotatable relativeto the stator. The prime mover outputs torque from the rotor by supplyof electric power to the prime mover.

The speed reducer reduces torque of the prime mover and outputs thereduced torque. The rotational translation unit includes a rotationportion that rotates relative to the housing upon receiving an input ofthe torque output from the speed reducer, and a translation portion thatmoves relative to the housing in an axial direction in accordance withrotation of the rotation portion relative to the housing.

The clutch is provided between a first transmission portion and a secondtransmission portion that are rotatable relative to the housing. Theclutch allows transmission of torque between the first transmissionportion and the second transmission portion in an engaged state of theclutch, and interrupts the transmission of torque between the firsttransmission portion and the second transmission portion in a disengagedstate of the clutch. The state changing unit receives a force along theaxial direction from the translation portion and changes a state of theclutch to the engaged state or the disengaged state according to aposition of the translation portion in the axial direction relative tothe housing.

The speed reducer includes a sun gear rotatable integrally with therotor, and a planetary gear configured to revolve in a circumferentialdirection of the sun gear while rotating in a state of meshing with thesun gear.

A gear width of the sun gear is set such that a meshing length betweenthe sun gear and the planetary gear is smaller than a gear width of theplanetary gear. Therefore, even if the planetary gear tilts with respectto the sun gear, a gap in a circumferential direction on a meshing pitchcircle between the sun gear and the planetary gears can be secured, andoccurrence of double-tooth meshing phenomenon between the sun gear andthe planetary gears can be reduced. Therefore, the speed reducer can bemaintained operating well.

Hereinafter, clutch devices according to multiple embodiments will bedescribed referring to drawings. In these embodiments, elements that aresubstantially same may be assigned the same reference numeral, andredundant explanation for the elements may be omitted.

First Embodiment

A clutch device according to a first embodiment is shown in FIGS. 1 and2. A clutch device 1 is provided, for example, between an internalcombustion engine and a transmission of a vehicle, and is used to allowor interrupt transmission of torque between the internal combustionengine and the transmission.

The clutch device 1 includes a housing 12, a motor 20 as a “primemover”, a speed reducer 30, a ball cam 2 as a “rotational translationunit” or a “rolling body cam”, a clutch 70, and a state changing unit80.

The clutch device 1 includes an electronic control unit (hereinafterreferred to as “ECU”) 10 as a “control unit”, an input shaft 61 as a“first transmission portion”, an output shaft 62 as a “secondtransmission portion”, and a fixing portion 130.

The ECU 10 is a small computer including a CPU as a calculation means, aROM, a RAM, and the like as storage means, an I/O as an input and outputmeans, and the like. The ECU 10 executes calculation according to aprogram stored in the ROM or the like based on information such assignals from various sensors provided in each part of the vehicle, andcontrols operations of various devices and machines of the vehicle. Inthis way, the ECU 10 executes the program stored in a non-transitorytangible storage medium. With the execution of the program, a methodcorresponding to the program is executed.

The ECU 10 can control an operation of the internal combustion engineand the like based on the information such as the signals from varioussensors. The ECU 10 can also control an operation of the motor 20 to bedescribed later.

The input shaft 61 is connected to, for example, a drive shaft (notshown) of the internal combustion engine, and is rotatable together withthe drive shaft. That is, torque is input to the input shaft 61 from thedrive shaft.

The vehicle equipped with the internal combustion engine is providedwith a fixing flange 11 (see FIG. 2). The fixing flange 11 is formed ina tubular shape, and is fixed to, for example, an engine compartment ofthe vehicle. A ball bearing 141 is provided between an inner peripheralwall of the fixing flange 11 and an outer peripheral wall of the inputshaft 61. Accordingly, the input shaft 61 is bearing-supported by thefixing flange 11 via the ball bearing 141.

The housing 12 is provided between an inner peripheral wall of an endportion of the fixing flange 11 and the outer peripheral wall of theinput shaft 61. The housing 12 includes a housing inner cylinder portion121, a housing plate portion 122, a housing outer cylinder portion 123,a housing flange portion 124, a housing step surface 125, a housing-sidespline groove portion 127, and the like.

The housing inner cylinder portion 121 is formed in a substantiallycylindrical shape. The housing plate portion 122 is formed in an annularplate shape so as to extend radially outward from an end portion of thehousing inner cylinder portion 121. The housing outer cylinder portion123 is formed in a substantially cylindrical shape so as to extend froman outer edge portion of the housing plate portion 122 to the same sideas the housing inner cylinder portion 121. The housing flange portion124 is formed in an annular plate shape so as to extend radially outwardfrom an end portion of the housing outer cylinder portion 123 oppositeto the housing plate portion 122. The housing inner cylinder portion121, the housing plate portion 122, the housing outer cylinder portion123, and the housing flange portion 124 are integrally formed of, forexample, metal.

The housing step surface 125 is formed in a circular-annular planarshape so as to face the side opposite to the housing plate portion 122on the radially outer side of the housing inner cylinder portion 121.The housing-side spline groove portion 127 is formed in an outerperipheral wall of the housing inner cylinder portion 121 so as toextend in an axial direction on a side opposite to the housing plateportion 122 with respect to the housing step surface 125. Multiplehousing-side spline groove portions 127 are formed in a circumferentialdirection of the housing inner cylinder portion 121.

The housing 12 is fixed to the fixing flange 11 such that a part of anouter wall of the housing 12 is in contact with a part of a wall surfaceof the fixing flange 11 (see FIG. 2). The housing 12 is fixed to thefixing flange 11 by a bolt or the like (not shown). The housing 12 isprovided coaxially with the fixing flange 11 and the input shaft 61. Asubstantially cylindrical space is formed between the inner peripheralwall of the housing inner cylinder portion 121 and the outer peripheralwall of the input shaft 61.

The housing 12 has an accommodation space 120. The accommodation space120 is defined by the housing inner cylinder portion 121, the housingplate portion 122, and the housing outer cylinder portion 123.

The fixing portion 130 includes a fixing cylinder portion 131, a fixingannular portion 132, and a fixing flange portion 133. The fixingcylinder portion 131 is formed in a substantially cylindrical shape. Thefixing annular portion 132 is formed in a substantially circular-annularshape so as to extend radially inward from an inner peripheral wall ofthe fixing cylinder portion 131. The fixing flange portion 133 is formedin a substantially circular-annular shape so as to extend radiallyoutward from an end portion of the fixing cylinder portion 131. Thefixing cylinder portion 131, the fixing annular portion 132, and thefixing flange portion 133 are integrally formed of, for example, metal.The fixing portion 130 is fixed to the housing 12 such that the fixingflange portion 133 is fixed to the housing flange portion 124 by a bolt13.

The motor 20 is accommodated in the accommodation space 120. The motor20 includes a stator 21, a coil 22, a rotor 23, and the like. The stator21 is formed in a substantially circular-annular shape by, for example,a laminated steel plate, and is fixed to an inside of the housing outercylinder portion 123. The coil 22 includes a bobbin 221 and a winding222. The bobbin 221 is formed of, for example, a resin in a cylindricalshape, and is fitted to multiple salient poles of the stator 21. Thewinding 222 is wound around the bobbin 221.

The rotor 23 includes a rotor cylinder portion 231, a rotor plateportion 232, and a rotor cylinder portion 233. The motor 20 includes amagnet 230 as a “permanent magnet”. The rotor cylinder portion 231 isformed in a substantially cylindrical shape. The rotor plate portion 232is formed in an annular plate shape so as to extend radially inward froman end portion of the rotor cylinder portion 231. The rotor cylinderportion 233 is formed in a substantially cylindrical shape so as toextend from an inner edge portion of the rotor plate portion 232 towarda side opposite to the rotor cylinder portion 231. The rotor cylinderportion 231, the rotor plate portion 232, and the rotor cylinder portion233 are integrally formed of, for example, iron-based metal. Morespecifically, the rotor 23 is formed of, for example, pure iron havingrelatively high magnetic properties.

The magnet 230 is provided on an outer peripheral wall of the rotorcylinder portion 231. Multiple magnets 230 are provided at equalintervals in a circumferential direction of the rotor cylinder portion231 such that the magnetic poles are alternately arranged.

The clutch device 1 includes a bearing portion 151. The bearing portion151 is provided on an outer peripheral wall on the housing plate portion122 side with respect to the housing step surface 125 of the housinginner cylinder portion 121. An inner peripheral wall of the bearingportion 151 is fitted to an outer peripheral wall of the housing innercylinder portion 121. The rotor 23 is provided such that an innerperipheral wall of the rotor cylinder portion 231 is fitted to an outerperipheral wall of the bearing portion 151. Accordingly, the rotor 23 isrotatably supported by the housing inner cylinder portion 121 via thebearing portion 151. Therefore, the bearing portion 151 is provided inthe accommodation space 120 and rotatably supports the rotor 23.

The rotor 23 is provided so as to be rotatable relatively with respectto the stator 21 on the radially inner side of the stator 21. The motor20 is an inner rotor type brushless DC motor.

The ECU 10 can control the operation of the motor 20 by controllingelectric power supplied to the winding 222 of the coil 22. When theelectric power is supplied to the coil 22, a rotating magnetic field isgenerated in the stator 21, and the rotor 23 rotates. Accordingly, thetorque is output from the rotor 23. As described above, the motor 20includes the stator 21 and the rotor 23 provided to be rotatablerelatively with respect to the stator 21, and is capable of outputtingthe torque from the rotor 23 by being supplied with electric power.

In the present embodiment, the clutch device 1 includes a substrate 101,a plate 102, a sensor magnet 103, and a rotation angle sensor 104. Thesubstrate 101, the plate 102, the sensor magnet 103, and the rotationangle sensor 104 are provided in the accommodation space 120. Thesubstrate 101 is provided on the outer peripheral wall of the housinginner cylinder portion 121 in the vicinity of the housing plate portion122. The plate 102 is formed in, for example, a substantiallycylindrical shape. An inner peripheral wall at one end of the plate 102is fitted to an outer peripheral wall of an end portion of the rotorcylinder portion 231 opposite to the rotor plate portion 232 so as to berotatable integrally with the rotor 23. The sensor magnet 103 is formedin a substantially circular-annular shape, and an inner peripheral wallof the sensor magnet 103 is fitted to an outer peripheral wall of theother end of the plate 102 so as to be rotatable integrally with theplate 102 and the rotor 23. The sensor magnet 103 generates a magneticflux.

The rotation angle sensor 104 is mounted on the substrate 101 so as toface a surface of the sensor magnet 103 opposite to the rotor 23. Therotation angle sensor 104 detects a magnetic flux generated from thesensor magnet 103 and outputs a signal corresponding to the detectedmagnetic flux to the ECU 10. Accordingly, the ECU 10 can detect arotation angle, a rotation speed, and the like of the rotor 23 based onthe signal from the rotation angle sensor 104. The ECU 10 can calculate,based on the rotation angle, the rotation speed, and the like of therotor 23, a relative rotation angle of a drive cam 40 with respect tothe housing 12 and a driven cam 50 to be described later, relativepositions of the driven cam 50 and the state changing unit 80 in theaxial direction with respect to the housing 12 and the drive cam 40, andthe like.

The speed reducer 30 is accommodated in the accommodation space 120. Thespeed reducer 30 includes a sun gear 31, planetary gears 32, a carrier33, a first ring gear 34, a second ring gear 35, and the like.

The sun gear 31 is provided coaxially with and integrally rotatable withthe rotor 23. That is, the rotor 23 and the sun gear 31 are formedseparately and coaxially disposed so as to be integrally rotatable. Morespecifically, the sun gear 31 is formed of, for example, metal in asubstantially cylindrical shape, and is fixed to the rotor 23 such thatan outer peripheral wall of one end portion of the sun gear 31 is fittedto an inner peripheral wall of the rotor cylinder portion 233. In thepresent embodiment, the sun gear 31 is joined to the rotor 23 by, forexample, press-fitting.

The sun gear 31 has a sun gear tooth portion 311 as “tooth portion” and“external teeth”. The sun gear tooth portion 311 is formed on the outerperipheral wall of the other end portion of the sun gear 31. The torqueof the motor 20 is input to the sun gear 31. The sun gear 31 correspondsto an “input portion” of the speed reducer 30. In the presentembodiment, the sun gear 31 is formed of, for example, a steel material.

Multiple planetary gears 32 are provided along the circumferentialdirection of the sun gear 31, and are each capable of revolving in thecircumferential direction of the sun gear 31 while rotating in a stateof meshing with the sun gear 31. More specifically, the planetary gears32 each are formed of, for example, metal in a substantially cylindricalshape, and four planetary gears 32 are provided at equal intervals inthe circumferential direction of the sun gear 31 on the radially outerside of the sun gear 31. The planetary gear 32 has a planetary geartooth portion 321 as “tooth portions” and “external teeth”. Theplanetary gear tooth portion 321 is formed on an outer peripheral wallof the planetary gear 32 so as to be able to mesh with the sun geartooth portion 311.

The carrier 33 rotatably supports the planetary gears 32 and isrotatable relatively with respect to the sun gear 31. More specifically,the carrier 33 is formed of, for example, metal in a substantiallycircular-annular shape, and is provided on the radially outer side withrespect to the sun gear 31. The carrier 33 is rotatable relatively withrespect to the rotor 23 and the sun gear 31.

The carrier 33 is provided with a pin 331, a needle bearing 332, and acarrier washer 333. The pin 331 is formed of, for example, metal in asubstantially columnar shape, and is provided on the carrier 33 so as topass through the inside of the planetary gear 32. The needle bearing 332is provided between an outer peripheral wall of the pin 331 and an innerperipheral wall of the planetary gear 32. Accordingly, the planetarygear 32 is rotatably supported by the pin 331 via the needle bearing332. The carrier washer 333 is formed of, for example, metal in anannular plate shape, and is provided between an end portion of theplanetary gear 32 and the carrier 33 on the radially outer side of thepin 331. Accordingly, the planetary gears 32 can smoothly rotaterelatively with respect to the carrier 33.

The first ring gear 34 has a first ring gear tooth portion 341, which isa tooth portion capable of meshing with the planetary gear 32, and isfixed to the housing 12. More specifically, the first ring gear 34 isformed of, for example, metal in a substantially circular-annular shape.The first ring gear 34 is integrally formed on an inner edge portion ofthe fixing annular portion 132 of the fixing portion 130. That is, thefirst ring gear 34 is fixed to the housing 12 via the fixing portion130. The first ring gear 34 is provided coaxially with the housing 12,the rotor 23, and the sun gear 31. The first ring gear tooth portion 341as the “tooth portion” and the “internal teeth” is formed on the inneredge portion of the first ring gear 34 so as to be able to mesh with oneaxial end portion of the planetary gear tooth portion 321 of theplanetary gear 32.

The second ring gear 35 has a second ring gear tooth portion 351 whichis a tooth portion capable of meshing with the planetary gear 32 and hasa different number of teeth from the first ring gear tooth portion 341,and is provided so as to be integrally rotatable with the drive cam 40to be described later. More specifically, the second ring gear 35 isformed of, for example, metal in a substantially circular-annular shape.The second ring gear 35 is provided coaxially with the housing 12, therotor 23, and the sun gear 31. The second ring gear tooth portion 351 asthe “tooth portion” and the “internal teeth” is formed on the inner edgeportion of the second ring gear 35 so as to be able to mesh with theother axial end portion of the planetary gear tooth portion 321 of theplanetary gear 32. In the present embodiment, the number of teeth of thesecond ring gear tooth portion 351 is larger than the number of teeth ofthe first ring gear tooth portion 341. More specifically, the number ofteeth of the second ring gear tooth portion 351 is larger than thenumber of teeth of the first ring gear tooth portion 341 by the numberobtained by multiplying 4, which is the number of the planetary gears32, by an integer.

Since the planetary gears 32 is required to normally mesh with the firstring gear 34 and the second ring gear 35 having two differentspecifications at the same portion without interference, the planetarygears 32 is designed such that one or both of the first ring gear 34 andthe second ring gear 35 are dislocated to keep a center distance of eachgear pair constant.

With the above configuration, when the rotor 23 of the motor 20 rotates,the sun gear 31 rotates, and the planetary gears 32 each revolve in thecircumferential direction of the sun gear 31 while rotating with theplanetary gear tooth portion 321 of the planetary gears 32 meshing withthe sun gear tooth portion 311, the first ring gear tooth portion 341,and the second ring gear tooth portion 351. Since the number of teeth ofthe second ring gear tooth portion 351 is larger than the number ofteeth of the first ring gear tooth portion 341, the second ring gear 35rotates relatively with respect to the first ring gear 34. Therefore, aminute differential rotation between the first ring gear 34 and thesecond ring gear 35 corresponding to a difference in the number of teethbetween the first ring gear tooth portion 341 and the second ring geartooth portion 351 is output as the rotation of the second ring gear 35.Accordingly, the torque from the motor 20 is reduced by the speedreducer 30 and is output from the second ring gear 35. In this way, thespeed reducer 30 can reduce the torque of the motor 20 and output thereduced torque. In the present embodiment, the speed reducer 30 forms a3k-type strange planetary gear speed reducer.

The second ring gear 35 is integrally formed with the drive cam 40 to bedescribed later. The second ring gear 35 reduces the torque from themotor 20 and outputs the reduced torque to the drive cam 40. The secondring gear 35 corresponds to an “output portion” of the speed reducer 30.

The ball cam 2 has the drive cam 40 as a “rotation portion”, the drivencam 50 as a “translation portion”, and a ball 3 as a “rolling body”.

The drive cam 40 includes a drive cam main body 41, a drive cam innercylinder portion 42, a drive cam plate portion 43, a drive cam outercylinder portion 44, drive cam grooves 400, and the like. The drive cammain body 41 is formed in a substantially circular-annular plate shape.The drive cam inner cylinder portion 42 is formed in a substantiallycylindrical shape so as to extend in the axial direction from an outeredge portion of the drive cam main body 41. The drive cam plate portion43 is formed in a substantially circular-annular plate shape so as toextend radially outward from an end portion of the drive cam innercylinder portion 42 opposite to the drive cam main body 41. The drivecam outer cylinder portion 44 is formed in a substantially cylindricalshape so as to extend from an outer edge portion of the drive cam plateportion 43 to the same side as the drive cam inner cylinder portion 42.The drive cam main body 41, the drive cam inner cylinder portion 42, thedrive cam plate portion 43, and the drive cam outer cylinder portion 44are integrally formed of, for example, metal.

The drive cam groove 400 is formed so as to extend in thecircumferential direction while being recessed from a surface of thedrive cam main body 41 on a drive cam inner cylinder portion 42 side.Five drive cam grooves 400 are formed at equal intervals in thecircumferential direction of the drive cam main body 41. The drive camgroove 400 is formed such that a groove bottom is inclined with respectto the surface of the drive cam main body 41 on the drive cam innercylinder portion 42 side such that a depth decreases from one end towardthe other end in the circumferential direction of the drive cam mainbody 41.

The drive cam 40 is provided inside the fixing portion 130 such that thedrive cam main body 41 is located between the outer peripheral wall ofthe housing inner cylinder portion 121 and the inner peripheral wall ofthe sun gear 31, the drive cam plate portion 43 is located on a sideopposite to the rotor 23 with respect to the carrier 33, and the drivecam outer cylinder portion 44 is located on a side opposite to thestator 21 with respect to the fixing annular portion 132 and inside thefixing cylinder portion 131. The drive cam 40 is rotatable relativelywith respect to the housing 12 and the fixing portion 130.

The second ring gear 35 is integrally formed with the inner edge portionof the drive cam outer cylinder portion 44. That is, the second ringgear 35 is provided so as to be integrally rotatable with the drive cam40 serving as the “rotation portion”. Therefore, when the torque fromthe motor 20 is reduced by the speed reducer 30 and is output from thesecond ring gear 35, the drive cam 40 rotates relatively with respect tothe housing 12 and the fixing portion 130. That is, when receiving thetorque output from the speed reducer 30, the drive cam 40 rotatesrelatively with respect to the housing 12.

The driven cam 50 has a driven cam main body 51, a driven cam cylinderportion 52, a driven cam step surface 53, a cam-side spline grooveportion 54, driven cam grooves 500, and the like. The driven cam mainbody 51 is formed in a substantially circular-annular plate shape. Thedriven cam cylinder portion 52 is formed in a substantially cylindricalshape so as to extend in the axial direction from an outer edge portionof the driven cam main body 51. The driven cam main body 51 and thedriven cam cylinder portion 52 are integrally formed of, for example,metal.

The driven cam step surface 53 is formed in a circular-annular planarshape on the radially outer side of the driven cam cylinder portion 52so as to face a side opposite to the driven cam main body 51. Thecam-side spline groove portion 54 is formed in an inner peripheral wallof the driven cam main body 51 so as to extend in the axial direction.Multiple cam-side spline groove portions 54 are formed in thecircumferential direction of the driven cam main body 51.

The driven cam 50 is provided such that the driven cam main body 51 islocated on a side opposite to the housing step surface 125 with respectto the drive cam main body 41 and on an inner side of the drive caminner cylinder portion 42, and the cam-side spline groove portion 54 isspline-coupled to the housing-side spline groove portion 127.Accordingly, the driven cam 50 is not rotatable relatively with respectto the housing 12 and is movable with respect to the housing 12 in theaxial direction.

The driven cam groove 500 is formed so as to extend in thecircumferential direction while being recessed from a surface of thedriven cam main body 51 on a side opposite to the driven cam cylinderportion 52. Five driven cam grooves 500 are formed at equal intervals inthe circumferential direction of the driven cam main body 51. The drivencam groove 500 is formed such that a groove bottom is inclined withrespect to a surface of the driven cam main body 51 opposite to thedriven cam cylinder portion 52 such that a depth of the driven camgroove 500 decreases from one end to the other end in thecircumferential direction of the driven cam main body 51.

The drive cam groove 400 and the driven cam groove 500 are formed tohave the same shape when viewed from a surface side of the drive cammain body 41 on the driven cam main body 51 side or a surface side ofthe driven cam main body 51 on the drive cam main body 41 side.

The ball 3 is formed in a spherical shape by, for example, metal. Theballs 3 are rollably provided between five drive cam grooves 400 andfive driven cam grooves 500, respectively. That is, a total of fiveballs 3 are provided.

In the present embodiment, the clutch device 1 includes a retainer 4.The retainer 4 is formed of, for example, metal in a substantiallycircular-annular plate shape, and is provided between the drive cam mainbody 41 and the driven cam main body 51. The retainer 4 has a holeportion having an inner diameter slightly larger than an outer diameterof the ball 3. Five hole portions are formed at equal intervals in thecircumferential direction of the retainer 4. The ball 3 is provided ineach of the five hole portions. Therefore, the balls 3 are held by theretainer 4, and positions of the balls 3 in the drive cam groove 400 andthe driven cam groove 500 are stabilized.

As described above, the drive cam 40, the driven cam 50, and the balls 3form the ball cam 2 as the “rolling body cam”. When the drive cam 40rotates relatively with respect to the housing 12 and the driven cam 50,the balls 3 roll respectively along the groove bottoms of the drive camgrooves 400 and the driven cam grooves 500.

As shown in FIG. 1, the balls 3 are provided on the radially inner sideof the first ring gear 34 and the second ring gear 35. Morespecifically, the balls 3 are provided within a range in the axialdirection of the first ring gear 34 and the second ring gear 35.

As described above, the drive cam groove 400 is formed such that thegroove bottom thereof is inclined from one end to the other end. Thedriven cam groove 500 is formed such that the groove bottom thereof isinclined from one end to the other end. Therefore, when the drive cam 40rotates relatively with respect to the housing 12 and the driven cam 50due to the torque output from the speed reducer 30, the balls 3 roll inthe drive cam grooves 400 and the driven cam grooves 500, and the drivencam 50 moves with respect to the drive cam 40 and the housing 12 in theaxial direction, that is, strokes.

When the drive cam 40 rotates relatively with respect to the housing 12,the driven cam 50 moves with respect to the drive cam 40 and the housing12 in the axial direction. The driven cam 50 does not rotate relativelywith respect to the housing 12 since the cam-side spline groove portion54 is spline-coupled to the housing-side spline groove portion 127. Thedrive cam 40 rotates relatively with respect to the housing 12, but doesnot move relatively with respect to the housing 12 in the axialdirection.

In the present embodiment, the clutch device 1 includes a return spring55, a return spring washer 56, and a C ring 57. The return spring 55 is,for example, a wave spring, and is provided between an outer peripheralwall of an end portion of the housing inner cylinder portion 121opposite to the housing plate portion 122 and an inner peripheral wallof the driven cam cylinder portion 52. One end of the return spring 55is in contact with an inner edge portion of a surface of the driven cammain body 51 on a driven cam cylinder portion 52 side.

The return spring washer 56 is formed of, for example, metal in asubstantially circular-annular shape, and is in contact with the otherend of the return spring 55 on the radially outer side of the housinginner cylinder portion 121. The C ring 57 is fixed to the outerperipheral wall of the housing inner cylinder portion 121 so as to locka surface of the return spring washer 56 opposite to the return spring55.

The return spring 55 has a force that extends in the axial direction.Therefore, the driven cam 50 is urged toward the drive cam main body 41by the return spring 55 in a state where the balls 3 are sandwichedbetween the driven cam 50 and the drive cam 40.

The output shaft 62 includes a shaft portion 621, a plate portion 622, acylinder portion 623, and a friction plate 624 (see FIG. 2). The shaftportion 621 is formed in a substantially cylindrical shape. The plateportion 622 is integrally formed with the shaft portion 621 so as toextend radially outward from one end of the shaft portion 621 in anannular plate shape. The cylinder portion 623 is integrally formed withthe plate portion 622 so as to extend in a substantially cylindricalshape from an outer edge portion of the plate portion 622 toward a sideopposite to the shaft portion 621. The friction plate 624 is formed in asubstantially circular-annular plate shape, and is provided on an endsurface of the plate portion 622 on a cylinder portion 623 side. Thefriction plate 624 is not rotatable relatively with respect to the plateportion 622. A clutch space 620 is formed inside the cylinder portion623.

An end portion of the input shaft 61 passes through the inside of thehousing inner cylinder portion 121 and is located on a side opposite tothe drive cam 40 with respect to the driven cam 50. The output shaft 62is provided coaxially with the input shaft 61 on a side opposite to thefixing flange 11 with respect to the housing 12, that is, on a sideopposite to the drive cam 40 with respect to the driven cam 50. A ballbearing 142 is provided between an inner peripheral wall of the shaftportion 621 and an outer peripheral wall of the end portion of the inputshaft 61. Accordingly, the output shaft 62 is bearing-supported by theinput shaft 61 via the ball bearing 142. The input shaft 61 and theoutput shaft 62 are rotatable relatively with respect to the housing 12.

The clutch 70 is provided in the clutch space 620 between the inputshaft 61 and the output shaft 62. The clutch 70 includes an innerfriction plate 71, an outer friction plate 72, and a locking portion701. Multiple inner friction plates 71 each are formed in asubstantially circular-annular plate shape, and are provided so as to bealigned in the axial direction between the input shaft 61 and thecylinder portion 623 of the output shaft 62. The inner friction plates71 are provided such that inner edge portions thereof are spline-coupledto the outer peripheral wall of the input shaft 61. Therefore, the innerfriction plates 71 are not rotatable relatively with respect to theinput shaft 61 and are movable with respect to the input shaft 61 in theaxial direction.

Multiple outer friction plates 72 each are formed in a substantiallycircular-annular plate shape, and are provided so as to be aligned inthe axial direction between the input shaft 61 and the cylinder portion623 of the output shaft 62. The inner friction plates 71 and the outerfriction plates 72 are alternately arranged in the axial direction ofthe input shaft 61. The outer friction plates 72 are provided such thatouter edge portions thereof are spline-coupled to an inner peripheralwall of the cylinder portion 623 of the output shaft 62. Therefore, theouter friction plates 72 is not rotatable relatively with respect to theoutput shaft 62 and is movable with respect to the output shaft 62 inthe axial direction. Among the multiple outer friction plates 72, theouter friction plate 72 located closest to the friction plate 624 iscontactable with the friction plate 624.

The locking portion 701 is formed in a substantially circular-annularshape, and is provided such that an outer edge portion is fitted intothe inner peripheral wall of the cylinder portion 623 of the outputshaft 62. The locking portion 701 can lock an outer edge portion of theouter friction plate 72 located closest to the driven cam 50 among themultiple outer friction plates 72. Therefore, the multiple outerfriction plates 72 and the multiple inner friction plates 71 areprevented from coming off from the inside of the cylinder portion 623. Adistance between the locking portion 701 and the friction plate 624 islarger than a sum of plate thicknesses of the multiple outer frictionplates 72 and the multiple inner friction plates 71.

In an engaged state in which the multiple inner friction plates 71 andthe multiple outer friction plates 72 are in contact with each other,that is, engaged with each other, a frictional force is generatedbetween the inner friction plates 71 and the outer friction plates 72,and relative rotation between the inner friction plates 71 and the outerfriction plates 72 is restricted according to a magnitude of thefrictional force. On the other hand, in a disengaged state in which themultiple inner friction plates 71 and the multiple outer friction plates72 are separated from each other, that is, are not engaged with eachother, no frictional force is generated between the inner frictionplates 71 and the outer friction plates 72, and the relative rotationbetween the inner friction plates 71 and the outer friction plates 72 isnot restricted.

When the clutch 70 is in the engaged state, the torque input to theinput shaft 61 is transmitted to the output shaft 62 via the clutch 70.On the other hand, when the clutch 70 is in the disengaged state, thetorque input to the input shaft 61 is not transmitted to the outputshaft 62.

In this way, the clutch 70 transmits the torque between the input shaft61 and the output shaft 62. The clutch 70 allows transmission of thetorque between the input shaft 61 and the output shaft 62 in the engagedstate in which the clutch 70 is engaged, and interrupts the transmissionof the torque between the input shaft 61 and the output shaft 62 in thedisengaged state in which the clutch 70 is not engaged.

In the present embodiment, the clutch device 1 is a so-called normallyopen clutch device that is normally in the disengaged state.

The state changing unit 80 includes a disk spring 81 as an “elasticdeformation portion”, a C ring 82, and a thrust bearing 83. The statechanging unit 80 includes two disk springs 81. The two disk springs 81are provided on the radially outer side of the driven cam cylinderportion 52 and on a side opposite to the driven cam main body 51 withrespect to the driven cam step surface 53 in a state where the disksprings 81 overlap each other in the axial direction.

The thrust bearing 83 is provided between the driven cam cylinderportion 52 and the disk spring 81. The thrust bearing 83 includes aroller 831, an inner ring portion 84, and an outer ring portion 85. Theinner ring portion 84 includes an inner ring plate portion 841 and aninner ring cylinder portion 842. The inner ring plate portion 841 isformed in a substantially circular-annular plate shape. The inner ringcylinder portion 842 is formed in a substantially cylindrical shape soas to extend from an inner edge portion of the inner ring plate portion841 toward one side in the axial direction. The inner ring plate portion841 and the inner ring cylinder portion 842 are integrally formed of,for example, metal. The inner ring portion 84 is provided such that theinner ring plate portion 841 is contactable with the driven cam stepsurface 53, and the inner peripheral wall of the inner ring cylinderportion 842 is contactable with the outer peripheral wall of the drivencam cylinder portion 52.

The outer ring portion 85 includes an outer ring plate portion 851, anouter ring cylinder portion 852, and an outer ring cylinder portion 853.The outer ring plate portion 851 is formed in a substantiallycircular-annular plate shape. The outer ring cylinder portion 852 isformed in a substantially cylindrical shape so as to extend from aninner edge portion of the outer ring plate portion 851 to one side inthe axial direction. The outer ring cylinder portion 853 is formed in asubstantially cylindrical shape so as to extend from an outer edgeportion of the outer ring plate portion 851 to the other side in theaxial direction. The outer ring plate portion 851, the outer ringcylinder portion 852, and the outer ring cylinder portion 853 areintegrally formed of, for example, metal. The outer ring portion 85 isprovided on the radially outer side of the driven cam cylinder portion52 on a side opposite to the driven cam step surface 53 with respect tothe inner ring portion 84. The two disk springs 81 are located on theradially outer side of the outer ring cylinder portion 852. The innerperipheral wall of the outer ring cylinder portion 852 is slidable onthe outer peripheral wall of the driven cam cylinder portion 52.

The roller 831 is provided between the inner ring portion 84 and theouter ring portion 85. The roller 831 is rollable between the inner ringplate portion 841 and the outer ring plate portion 851. Accordingly, theinner ring portion 84 and the outer ring portion 85 are rotatablerelatively with respect to each other.

One disk spring 81 in the two disk springs 81 is provided such that oneend thereof in the axial direction, that is, an inner edge portionthereof is contactable with the outer ring plate portion 851. The C ring82 is fixed to the outer peripheral wall of the driven cam cylinderportion 52 so as to be able to lock one end in the axial direction ofthe other disk spring 81 in the two disk springs 81 and an end portionof the outer ring cylinder portion 852. Therefore, the two disk springs81 and the thrust bearing 83 are prevented from coming off from thedriven cam cylinder portion 52 by the C ring 82. The disk spring 81 iselastically deformable in the axial direction.

When the ball 3 is located at one end of the drive cam groove 400 andthe driven cam groove 500, a distance between the drive cam 40 and thedriven cam 50 is relatively small, and a gap Sp1 is formed between theclutch 70 and the other end in the axial direction of the other diskspring 81 in the two disk springs 81, that is, the outer edge portion(see FIG. 1). Therefore, the clutch 70 is in the disengaged state, andtransmission of torque between the input shaft 61 and the output shaft62 is interrupted.

When electric power is supplied to the coil 22 of the motor 20 under thecontrol of the ECU 10, the motor 20 rotates, the torque is output fromthe speed reducer 30, and the drive cam 40 rotates relatively withrespect to the housing 12. Accordingly, the ball 3 rolls from one end tothe other end of the drive cam groove 400 and the driven cam groove 500.Therefore, the driven cam 50 moves relatively with respect to thehousing 12 in the axial direction, that is, moves toward the clutch 70while compressing the return spring 55. Accordingly, the disk springs 81move toward the clutch 70.

When the disk springs 81 move toward the clutch 70 due to the movementof the driven cam 50 in the axial direction, the gap Sp1 reduces, andthe other end in the axial direction of the other disk spring 81 in thetwo disk springs 81 comes into contact with the outer friction plate 72of the clutch 70. When the driven cam 50 further moves in the axialdirection after the disk spring 81 comes into contact with the clutch70, the disk spring 81 presses the outer friction plate 72 toward afriction plate 624 side while being elastically deformed in the axialdirection. Accordingly, the multiple inner friction plates 71 and themultiple outer friction plates 72 are engaged with each other, and theclutch 70 is brought into the engaged state. The torque transmissionbetween the input shaft 61 and the output shaft 62 is allowed.

At this time, the two disk springs 81 rotate relatively with respect tothe driven cam cylinder portion 52 together with the outer ring portion85 of the thrust bearing 83. At this time, the roller 831 rolls betweenthe inner ring plate portion 841 and the outer ring plate portion 851while receiving a load in a thrust direction from the disk spring 81.The thrust bearing 83 bearing-supports the disk spring 81 whilereceiving the load in the thrust direction from the disk spring 81.

When a clutch transmission torque reaches a clutch required torquecapacity, the ECU 10 stops the rotation of the motor 20. Accordingly,the clutch 70 is in an engagement maintaining state in which the clutchtransmission torque is maintained at the clutch required torquecapacity. As described above, the disk springs 81 of the state changingunit 80 receives a force in the axial direction from the driven cam 50,and can change the state of the clutch 70 to the engaged state or thedisengaged state according to a relative position of the driven cam 50in the axial direction with respect to the housing 12 and the drive cam40.

In the output shaft 62, an end portion of the shaft portion 621 oppositeto the plate portion 622 is connected to an input shaft of atransmission (not shown), and the output shaft 62 is rotatable togetherwith the input shaft. That is, the torque output from the output shaft62 is input to the input shaft of the transmission. The torque input tothe transmission is changed in speed by the transmission, and is outputto driving wheels of the vehicle as a drive torque. Accordingly, thevehicle travels.

Next, a 3k-type strange planetary gear speed reducer adopted by thespeed reducer 30 according to the present embodiment will be described.

In an electric clutch device as in the present embodiment, it isrequired to shorten a time required for an initial response to reduce aninitial gap (corresponding to the gap Sp1) between the clutch and anactuator. It can be seen from an equation of rotation motion that it issufficient to reduce an inertia moment around the input shaft in orderto speed up the initial response. The inertia moment in a case where theinput shaft is a solid cylindrical member increases in proportion to afourth power of an outer diameter when compared with constant length anddensity. In the clutch device 1 according to the present embodiment, thesun gear 31 corresponding to the “input shaft” here is a hollowcylindrical member, whereas a tendency does not change.

An upper part in FIG. 3 shows a schematic diagram of a 2kh-type strangeplanetary gear speed reducer. An upper part in FIG. 4 shows a schematicdiagram of the 3k-type strange planetary gear speed reducer. The sungear is denoted by A. The planetary gear is denoted by B. The first ringgear is denoted by C. The second ring gear is denoted by D. The carrieris denoted by S. Comparing the 2kh-type and the 3k-type, the 3k-type hasa configuration in which the sun gear A is added to the 2kh-type.

In the case of the 2kh-type, the inertia moment around the input shaftis smallest when the carrier S located on a radially innermost sideamong constituent elements is used as an input element (see a table in alower part of FIG. 3).

On the other hand, in the case of the 3kh-type, the inertia momentaround the input shaft is smallest when the sun gear A located on theradially innermost side among the constituent elements is used as theinput element (see a table in a lower part of FIG. 4).

A magnitude of the inertia moment is larger in the case where thecarrier S is used as the input element in the 2kh-type than in the casewhere the sun gear A is used as the input element in the 3kh-type.Therefore, in the electric clutch device in which the speed of theinitial response is required, when a strange planetary gear reducer isadopted as the speed reducer, it is desirable to use the 3k-type and usethe sun gear A as the input element.

Further, in the electric clutch device, the required load is as large asseveral thousands to several tens of thousands N, and in order toachieve both a high response and a high load, it is necessary toincrease a speed reduction ratio of the speed reducer. When maximumspeed reduction ratios of the 2kh-type and the 3k-type are compared witheach other in the same gear specification, the maximum speed reductionratio of the 3k-type is large than and is about twice the maximum speedreduction ratio of the 2kh-type. In the case of the 3k-type, a largespeed reduction ratio can be obtained when the sun gear A having thesmallest inertia moment is used as an input element (see the table inthe lower part of FIG. 4). Therefore, it can be said that an optimalconfiguration for achieving both high response and high load is aconfiguration in which the 3k-type is used and the sun gear A is used asthe input element.

In the present embodiment, the speed reducer 30 is a 3k-type strangeplanetary gear speed reducer having the sun gear 31 (A) as the inputelement, the second ring gear 35 (D) as an output element, and the firstring gear 34 (C) as a fixing element. Therefore, the inertia momentaround the sun gear 31 can be reduced, and the speed reduction ratio ofthe speed reducer 30 can be increased. It is possible to achieve bothhigh response and high load in the clutch device 1.

Next, an effect of the state changing unit 80 having the disk spring 81as the elastic deformation portion will be described.

As shown in FIG. 5, with respect to a relationship between the movementof the driven cam 50 in the axial direction, that is, a stroke and aload acting on the clutch 70, when comparing a configuration in whichthe clutch 70 is pushed by a rigid body that is difficult to elasticallydeform in the axial direction (see an alternate long and short dash linein FIG. 5) and a configuration in which the clutch 70 is pushed by thedisk spring 81 that is elastically deformable in the axial direction asin the present embodiment (see a solid line in FIG. 5), it can be seenthat, when variations in the stroke are the same, a variation in theload acting on the clutch 70 is smaller in the configuration in whichthe clutch 70 is pushed by the disk spring 81 than that in theconfiguration in which the clutch 70 is pushed by the rigid body. Thisis because, as compared with the configuration in which the clutch 70 ispushed by the rigid body, a combined spring constant can be reduced byusing the disk spring 81, so that the variation in the load with respectto the variation in the stroke of the driven cam 50 caused by theactuator can be reduced. In the present embodiment, since the statechanging unit 80 includes the disk spring 81 as the elastic deformationportion, the variation in the load with respect to the variation in thestroke of the driven cam 50 can be reduced, and a target load can beeasily applied to the clutch 70.

Hereinafter, the configuration of each portion according to the presentembodiment will be described in more detail.

As shown in FIG. 6, in the present embodiment, a gear width L3, which isa length in the axial direction of the sun gear tooth portion 311 of thesun gear 31, is set such that a meshing length L2 between the sun gear31 and the planetary gear 32, which is a length in the axial directionby which the sun gear tooth portion 311 and the planetary gear toothportion 321 overlap, i.e. mesh with each other, is smaller than a gearwidth L1, which is a length in the axial direction of the planetary geartooth portion 321 of the planetary gear 32. That is, the sun gear 31 isprovided and formed such that the meshing length L2 between the sun gear31 and the planetary gear 32 is smaller than the gear width L1 of theplanetary gear 32.

In the present embodiment, the gear width L3 of the sun gear 31 issmaller than the gear width L1 of the planetary gear 32. Therefore,regardless of the positions of the sun gear 31 and the planetary gear 32in the axial direction of the sun gear 31, the meshing length L2 betweenthe sun gear 31 and the planetary gear 32 is smaller than the gear widthL1 of the planetary gear 32.

In the present embodiment, the meshing length L2 between the sun gear 31and the planetary gear 32 is set to about 50% of the gear width L1 ofthe planetary gear 32. The meshing length L2 between the sun gear 31 andthe planetary gear 32 is preferably set to 20% to 50% of the gear widthL1 of the planetary gear 32.

Hereinafter, a more detailed configuration, operation, and the like willbe described.

As shown in FIG. 7, when torque MA is applied to the sun gear 31 in astate where load torque MD is applied to the second ring gear 35, amoment generated around an axis A×P of the planetary gear 32 is zero dueto three forces including a force FD acting on the planetary gear 32 bythe load torque MD of the second ring gear 35, a force FA acting on theplanetary gear 32 by the torque MA, and a force FC acting on theplanetary gear 32 by load torque MC of the first ring gear 34, and abalance of the planetary gear 32 is maintained.

As shown in FIGS. 7 and 8, the force FC and the force FD acting on theplanetary gear tooth portion 321 are in a twisted relationship.Therefore, in a range of a gap between the planetary gear tooth portion321 and the first ring gear tooth portion 341 and a gap between theplanetary gear tooth portion 321 and the second ring gear tooth portion351, a moment is generated to rotate the planetary gear 32 in adirection R0 in which the axis A×P is inclined. Accordingly, theplanetary gear 32 may rotate with respect to the carrier 33 such thatthe axis A×P is inclined.

The carrier 33 may rotate in a direction R1, a direction R2, a directionR3, a direction R4, and the like (see FIG. 9) due to, for example, anaxial gap SpA which is a gap in the axial direction between the carrier33 and the rotor 23 which is another member and a radial gap SpR whichis a gap in the radial direction (see FIG. 6). The rotation is added tothe rotation of the planetary gears 32 in the direction R0, and theplanetary gears 32 may rotate and incline greatly with respect tomembers other than the carrier 33 (see dashed lines in FIG. 9).

When the planetary gears 32 are inclined with respect to the sun gear31, the clearance formed between the sun gear tooth portion 311 of thesun gear 31 and the planetary gear tooth portion 321 of the planetarygear 32 before the inclination is reduced by an amount proportional tothe meshing width and the inclination angle between the sun gear 31 andthe planetary gear 32. When the clearance is zero, a so-calleddouble-tooth meshing phenomenon occurs between the sun gear 31 and theplanetary gear 32.

As shown in FIG. 10, in the present embodiment, the sun gear 31 and theplanetary gear 32 are formed such that C−L2·tan α≥0 and L1>L2, wherein Cis a backlash in a circumferential direction on a meshing pitch circleCp1 between the sun gear 31 and the planetary gear 32 when theinclination angle of the planetary gears 32 with respect to the sun gear31 is 0, α is an inclination angle of the planetary gear 32 with respectto the sun gear 31, L1 is a gear width of the planetary gear 32, and L2is a meshing length between the sun gear 31 and the planetary gear 32.That is, in the present embodiment, C, α, L1, and L2 are set such thatC−L2·tan α≥0 and L1>L2.

As shown in FIG. 11, C−L2·tan α, which is a remaining gap between thesun gear tooth portion 311 and the planetary gear tooth portion 321 whenthe inclination angle of the planetary gear 32 with respect to the sungear 31 is a, decreases as the meshing length L2 between the sun gear 31and the planetary gear 32 increases. When the remaining gap C−L2·tan αis 0, the sun gear tooth portion 311 and the planetary gear toothportion 321 interfere with each other. That is, a condition ofoccurrence of interference is C−L2·tan α<0.

In FIG. 10, the sun gear tooth portion 312 in a comparative example isindicated by a two-dot chain line. A gear width and a meshing lengthwith the planetary gear 32 of the sun gear tooth portion 312 are L1,that is, the same as the gear width L1 of the planetary gear 32. In thecase of the comparative embodiment, even if the inclination angle α ofthe planetary gear 32 with respect to the sun gear 31 is relativelysmall, both ends of the planetary gear tooth portion 321 in the axis A×Pdirection come into contact with the adjacent sun gear tooth portions312, and the double-tooth meshing phenomenon occurs (see FIG. 10).

On the other hand, as described above, the sun gear 31 and the planetarygear 32 according to the present embodiment are formed such thatC−L2·tan α≥0 and L1>L2. Therefore, when the inclination angle α of theplanetary gear 32 with respect to the sun gear 31 is about the same asthat in the example of the comparative embodiment, both ends of theplanetary gear tooth portion 321 in the axis A×P direction do not comeinto contact with the adjacent sun gear tooth portions 311, and theoccurrence of the double-tooth meshing phenomenon can be prevented.

In the comparative embodiment, in order to prevent the interferencebetween the sun gear tooth portion 312 and the planetary gear toothportion 321, countermeasures such as (1) “reduce a” and (2) “reducetooth thicknesses of the sun gear tooth portion 311 and the planetarygear tooth portion 321” are considered.

(1) In order to “reduce a”, it is conceivable to reduce the axial gapSpA and the radial gap SpR between the carrier 33 and the rotor 23.However, in this case, it is necessary to improve processing accuracy ofthe members, which may lead to an increase in cost.

(2) “Reducing the tooth thicknesses of the sun gear tooth portion 311and the planetary gear tooth portion 321” may cause performancedisadvantages such as a reduction in bending strength of a tooth rootand an increase in backlash and tooth hitting noise.

On the other hand, in the present embodiment, the sun gear 31 and theplanetary gear 32 are formed such that the meshing length L2 between thesun gear 31 and the planetary gear 32 is smaller than the gear width L1of the planetary gear 32, that is, L1>L2. Therefore, the interferencebetween the sun gear tooth portion 311 and the planetary gear toothportion 321 can be prevented without causing the above-describedproblems of the countermeasures (1) and (2).

In the present embodiment, although a contact area between the sun geartooth portion 311 and the planetary gear tooth portion 321 may bereduced and surface pressure may be increased by setting L1>L2, a3k-type strange planetary gear speed reducer is employed, and the torqueapplied to the sun gear 31 is small, so that there is no problem instrength even if the meshing length L2 is reduced to half, that is,about 50% of the gear width L1 of the planetary gear 32.

The motor 20 includes the magnet 230 as the “permanent magnet” providedin the rotor 23 (see FIG. 6). The magnet 230 is provided on the outerperipheral wall of the rotor 23. That is, the motor 20 is a surfacemagnet type (SPM) motor.

In the present embodiment, the clutch device 1 includes an oil supplyportion (not shown). The oil supply portion is formed in a passage shapein the output shaft 62 such that one end of the oil supply portion 5 isexposed to the clutch space 620. The other end of the oil supply portionis connected to an oil supply source (not shown). Accordingly, oil issupplied from one end of the oil supply portion to the clutch 70 in theclutch space 620.

The ECU 10 controls an amount of oil to be supplied from the oil supplyportion to the clutch 70. The oil supplied to the clutch 70 canlubricate and cool the clutch 70. In the present embodiment, the clutch70 is a wet clutch and can be cooled by oil.

In the present embodiment, the ball cam 2 as the “rotational translationunit” forms the accommodation space 120 between the drive cam 40 as the“rotation portion” and the housing 12. The accommodation space 120 isformed inside the housing 12 on a side opposite to the clutch 70 withrespect to the drive cam 40. The motor 20 and the speed reducer 30 areprovided in the accommodation space 120.

The clutch 70 is provided in the clutch space 620, which is a spaceopposite to the accommodation space 120 with respect to the drive cam40.

In the present embodiment, the clutch device 1 includes an inner sealingmember 401 and an outer sealing member 402 as “seal members”. The innersealing member 401 and the outer sealing member 402 are formed in anannular shape using an elastic material such as rubber.

The inner sealing member 401 and the outer sealing member 402 areso-called O-rings. An inner diameter and an outer diameter of the innersealing member 401 are smaller than an inner diameter and an outerdiameter of the outer sealing member 402.

The inner sealing member 401 is provided in an annular seal grooveportion 128 formed in the outer peripheral wall of the housing innercylinder portion 121 between the housing-side spline groove portion 127and the housing step surface 125. The outer sealing member 402 isprovided in an annular seal groove portion 441 formed in the outerperipheral wall of the drive cam outer cylinder portion 44. That is, theouter sealing member 402 is provided so as to be in contact with thedrive cam 40 on the radially outer side of the drive cam 40 as the“rotation portion”.

The inner peripheral wall of the drive cam main body 41 is slidable withrespect to an outer edge portion of the inner sealing member 401. Thatis, the inner sealing member 401 is provided so as to be in contact withthe drive cam 40 on the radially inner side of the drive cam 40 as the“rotation portion”. The inner sealing member 401 seals the housing innercylinder portion 121 and the inner peripheral wall of the drive cam mainbody 41 in an airtight or liquid-tight manner while being elasticallydeformed in the radial direction.

The outer sealing member 402 is provided so as to be located on theradially outer side of the inner sealing member 401 when viewed in theaxial direction of the inner sealing member 401 (see FIGS. 1 and 2).

The inner peripheral wall of the fixing cylinder portion 131 is slidablewith respect to an outer edge portion of the outer sealing member 402.That is, the outer sealing member 402 is provided so as to be in contactwith the fixing cylinder portion 131 of the fixing portion 130. Theouter sealing member 402 seals the drive cam outer cylinder portion 44and the inner peripheral wall of the fixing cylinder portion 131 in anairtight or liquid-tight manner while being elastically deformed in theradial direction.

By the inner sealing member 401 and the outer sealing member 402provided as described above, an airtight or liquid-tight state can bemaintained between the accommodation space 120 in which the motor 20 andthe speed reducer 30 are accommodated and the clutch space 620 in whichthe clutch 70 is provided. Accordingly, for example, even if a foreignmatter such as the abrasion powder is generated in the clutch 70, theforeign matter can be prevented from entering the accommodation space120 from the clutch space 620. Therefore, operation failure of the motor20 or the speed reducer 30 caused by the foreign matter can beprevented.

In the present embodiment, since the airtight or liquid-tight state ismaintained between the accommodation space 120 and the clutch space 620by the inner sealing member 401 and the outer sealing member 402, evenif the foreign matter such as abrasion powder is contained in the oilsupplied to the clutch 70, the oil containing the foreign matter can beprevented from flowing from the clutch space 620 into the accommodationspace 120.

In the present embodiment, the housing 12 is formed in a closed shapefrom a portion corresponding to the radially outer side of the outersealing member 402 to a portion corresponding to the radially inner sideof the inner sealing member 401 (see FIGS. 1 and 2).

In the present embodiment, the drive cam 40 that forms the accommodationspace 120 with the housing 12 rotates relatively with respect to thehousing 12, but does not move with respect to the housing 12 in theaxial direction. Therefore, during an operation of the clutch device 1,a change in a volume of the accommodation space 120 can be prevented,and generation of negative pressure in the accommodation space 120 canbe prevented. Accordingly, oil or the like containing the foreign mattercan be prevented from being suctioned into the accommodation space 120from the clutch space 620 side.

The inner sealing member 401 in contact with the inner edge portion ofthe drive cam 40 slides with respect to the drive cam 40 in thecircumferential direction, but does not slide in the axial direction.The outer sealing member 402 that is in contact with the innerperipheral wall of the fixing cylinder portion 131 of the fixing portion130 slides with respect to the fixing portion 130 in the circumferentialdirection, but does not slide in the axial direction.

As shown in FIG. 1, the drive cam main body 41 is located on a sideopposite to the clutch 70 with respect to a surface of the drive camouter cylinder portion 44 on the side opposite to the clutch 70. Thatis, the drive cam 40 as the “rotation portion” is bent in the axialdirection so as to be formed such that the drive cam main body 41, whichis the inner edge portion of the drive cam 40, and the drive cam outercylinder portion 44, which is the outer edge portion of the drive cam40, are formed at different positions in the axial direction.

The driven cam main body 51 is provided so as to be located on a clutch70 side of the drive cam main body 41 and on the radially inner side ofthe drive cam inner cylinder portion 42. That is, the drive cam 40 andthe driven cam 50 are provided in a nested manner in the axialdirection.

More specifically, the driven cam main body 51 is located on theradially inner side of the drive cam outer cylinder portion 44, thesecond ring gear 35, and the drive cam inner cylinder portion 42. Thesun gear tooth portion 311 of the sun gear 31, the carrier 33, and theplanetary gears 32 are located on the radially outer side of the drivecam main body 41 and the driven cam main body 51. Accordingly, a size inthe axial direction of the clutch device 1 including the speed reducer30 and the ball cam 2 can be significantly reduced.

In the present embodiment, as shown in FIG. 1, in the axial direction ofthe drive cam main body 41, the drive cam main body 41, the sun gear 31,the carrier 33, and the bobbin 221 and the winding 222 of the coil 22are disposed so as to partially overlap each other. In other words, thecoil 22 is provided such that a part of the coil 22 is located on theradially outer side of a part of the drive cam main body 41, the sungear 31, and the carrier 33 in the axial direction. Accordingly, thesize of the clutch device 1 in the axial direction can be furtherreduced.

In the present embodiment, the clutch device 1 includes a thrust bearing161 and a thrust bearing washer 162. The thrust bearing washer 162 isformed of, for example, metal in a substantially circular-annular plateshape, and is provided such that one surface thereof is in contact withthe housing step surface 125. The thrust bearing 161 is provided betweenthe other surface of the thrust bearing washer 162 and a surface of thedrive cam main body 41 opposite to the driven cam 50. The thrust bearing161 bearing-supports the drive cam 40 while receiving a load in thethrust direction from the drive cam 40. In the present embodiment, theload in the thrust direction acting on the drive cam 40 from the clutch70 side via the driven cam 50 acts on the housing step surface 125 viathe thrust bearing 161 and the thrust bearing washer 162. Therefore, thedrive cam 40 can be stably bearing-supported by the housing step surface125.

As described above, in the present embodiment, the gear width L3 of thesun gear 31 is set such that the meshing length L2 between the sun gear31 and the planetary gear 32 is smaller than the gear width L1 of theplanetary gear 32. Therefore, even if the planetary gear 32 is inclinedwith respect to the sun gear 31, the gap in the circumferentialdirection on the meshing pitch circle Cp1 between the sun gear 31 andthe planetary gear 32 can be secured, and occurrence of the double-toothmeshing phenomenon between the sun gear 31 and the planetary gear 32 canbe prevented. Therefore, the speed reducer 30 can be maintainedoperating well.

In the present embodiment, the meshing length L2 between the sun gear 31and the planetary gear 32 is set to about 50% of the gear width L1 ofthe planetary gear 32.

Therefore, the meshing length L2 between the sun gear 31 and theplanetary gear 32 can be reliably set to be smaller than the gear widthL1 of the planetary gear 32. In the present embodiment, the 3k-typestrange planetary gear speed reducer is employed, and the torque appliedto the sun gear 31 is small, so that there is no problem in strengtheven if the meshing length L2 is about 50% of the gear width L1 of theplanetary gear 32.

In the present embodiment, the sun gear 31 and the planetary gear 32 areformed such that C−L2·tan α≥0 and L1>L2, wherein C is the backlash inthe circumferential direction on the meshing pitch circle Cp1 betweenthe sun gear 31 and the planetary gear 32 when the inclination angle ofthe planetary gear 32 with respect to the sun gear 31 is 0, α is theinclination angle of the planetary gear 32 with respect to the sun gear31, L1 is the gear width of the planetary gear 32, and L2 is the meshinglength between the sun gear 31 and the planetary gear 32.

Therefore, the occurrence of the double-tooth meshing phenomenon betweenthe sun gear 31 and the planetary gear 32 can be reliably prevented.

In the present embodiment, the motor 20 includes the magnet 230 providedin the rotor 23. That is, the motor 20 is a brushless DC motor using themagnet 230 as the “permanent magnet”.

In the present embodiment, the inner sealing member 401 and the outersealing member 402 can maintain a liquid-tight state between theaccommodation space 120 and the clutch space 620. Accordingly, even ifmagnetic particles such as iron powder are contained in the oil suppliedto the clutch 70 for cooling the clutch 70, it is possible to preventthe oil containing the magnetic particles from flowing from the clutchspace 620 into the accommodation space 120. Therefore, the magneticparticles can be prevented from being absorbed to the magnet 230 of themotor 20, and the decrease in the rotation performance of the motor 20and the operation failure can be prevented.

In the present embodiment, the speed reducer 30 includes the carrier 33,the first ring gear 34, and the second ring gear 35.

The carrier 33 rotatably supports the planetary gears 32 and isrotatable relatively with respect to the sun gear 31. The first ringgear 34 can mesh with the planetary gears 32. The second ring gear 35 isformed so as to be capable of meshing with the planetary gears 32 andsuch that the number of teeth of the tooth portion of the second ringgear 35 is different from that of the first ring gear 34, and outputstorque to the drive cam 40 of the ball cam 2.

In the present embodiment, the speed reducer 30 corresponds to aconfiguration of a number of strange planetary gear reducers and aconfiguration of a highest response and a highest load among the inputand output patterns. Therefore, both high response and high load of thespeed reducer 30 can be achieved.

In the present embodiment, as described above, the inner sealing member401 and the outer sealing member 402 can maintain a liquid-tight statebetween the accommodation space 120 and the clutch space 620.Accordingly, it is possible to reduce the influence of oil containingfine iron powder on the speed reducer 30 as the “strange planetary gearreducer” having many meshing portions, for example, damage, wear, adecrease in principle efficiency, and the like.

In the present embodiment, the first ring gear 34 is fixed to thehousing 12. The second ring gear 35 is provided so as to be integrallyrotatable with the drive cam 40.

In the present embodiment, responsiveness of the clutch device 1 can beimproved by connecting the components, as described above, such that theinertia moment of a high-speed rotation portion of the speed reducer 30as the “strange planetary gear speed reducer” is reduced.

In the present embodiment, the drive cam 40 is formed integrally withthe second ring gear 35. Therefore, the number of members and the numberof assembling steps can be reduced, and further cost reduction can beachieved.

In the present embodiment, the “rotation portion” of the “rotationaltranslation unit” is the drive cam 40 having the multiple drive camgrooves 400 formed on one surface in the axial direction. The“translation portion” is the driven cam 50 having the multiple drivencam grooves 500 formed on one surface in the axial direction. The“rotational translation unit” is the ball cam 2 including the drive cam40, the driven cam 50, and the balls 3 each provided so as to berollable between the drive cam groove 400 and the driven cam groove 500.

Therefore, the efficiency of the “rotational translation unit” can beimproved as compared with a case where the “rotational translation unit”is configured by, for example, a “sliding screw”. As compared with acase where the “rotational translation unit” is configured by, forexample, a “ball screw”, it is possible to reduce the cost, to reducethe size of the “rotational translation unit” in the axial direction,and to further reduce the size of the clutch device.

In the present embodiment, the drive cam 40 as the “rotation portion” isformed such that the drive cam main body 41, which is the inner edgeportion, and the drive cam outer cylinder portion 44, which is the outeredge portion, are located at different positions in the axial direction.

Therefore, the drive cam 40, the driven cam 50 as the “translationportion”, and the speed reducer 30 can be disposed in a nested manner inthe axial direction, and the size of the clutch device 1 in the axialdirection can be reduced.

In the present embodiment, the motor 20 and the speed reducer 30 areprovided in the accommodation space 120 formed inside the housing 12 onthe side opposite to the clutch 70 with respect to the drive cam 40. Theclutch 70 is provided in the clutch space 620, which is a space oppositeto the accommodation space 120 with respect to the drive cam 40.

The inner sealing member 401 and the outer sealing member 402 as the“sealing members” are each formed in an annular shape, are provided soas to be in contact with the drive cam 40 as the “rotation portion”, andcan maintain an airtight or liquid-tight state between the accommodationspace 120 and the clutch space 620.

Accordingly, for example, even if a foreign matter such as the abrasionpowder is generated in the clutch 70, the foreign matter can beprevented from entering the accommodation space 120 from the clutchspace 620. Therefore, operation failure of the motor 20 or the speedreducer 30 caused by the foreign matter can be prevented. Therefore, theoperation failure of the clutch device 1 caused by foreign matter can beprevented.

In the present embodiment, the inner sealing member 401 and the outersealing member 402 as the “sealing members” are disposed so as to be incontact with the drive cam 40 as the “rotation portion”, and maintainthe airtight or liquid-tight state between the accommodation space 120and the clutch space 620. Therefore, oil or the like containing fineiron powder or the like can be prevented from entering the accommodationspace 120 accommodating the motor 20 and the speed reducer 30, and agood performance of the clutch device 1 can be maintained for a longperiod of time.

In the present embodiment, the inner sealing member 401 and the outersealing member 402 are provided so as to be in contact with the drivecam 40, which is a component that is reduced by the speed reducer 30 andamplified to a large drive torque. Therefore, a ratio of a loss torqueassociated with the sealing performed by the “sealing members” to thewhole torque reduces, which is advantageous in terms of efficiency. In acase where the “sealing members” are provided so as to be in contactwith the rotor 23 which is a component on the input side of the speedreducer 30, the loss torque due to the “sealing members” is lost withrespect to small drive torque, and thus the efficiency may besignificantly reduced.

In the present embodiment, in a flow path of a power, an upstream sideof the drive cam 40 is set as the accommodation space 120, and theaccommodation space 120 is sealed by the inner sealing member 401 andthe outer sealing member 402. The inner sealing member 401 and the outersealing member 402 rotate relatively with respect to the housing 12together with the drive cam 40, but do not move with respect to thehousing 12 in the axial direction. Therefore, even when the drive cam 40rotates, the volume of the accommodation space 120 does not change.Accordingly, there is no influence in the change in a spatial volumecaused by a translational motion of the driven cam 50 as the“translation portion”, and a special volume change absorbing means suchas a bellows-shaped sealing member described in, for example, US PatentApplication Publication No. 2015/0144453 is not necessary.

In the present embodiment, the inner sealing member 401 and the outersealing member 402 as the “sealing members” are O-rings.

Therefore, the configuration of the clutch device 1 can be simplifiedand reduced in cost.

In the present embodiment, the state changing unit 80 includes the diskspring 81 as the “elastic deformation portion” that is elasticallydeformable in the axial direction of the driven cam 50 as the“translation portion”.

By controlling a rotation angle position of the motor 20, thrust controlof the clutch 70 can be performed with high accuracy based on thedisplacement and load characteristics of the disk spring 81. Therefore,the variation in the load acting on the clutch 70 with respect to thevariation in the stroke of the driven cam 50 can be reduced.Accordingly, the load control can be performed with high accuracy, andthe clutch device 1 can be controlled with high accuracy.

Second Embodiment

A clutch device according to a second embodiment is shown in FIG. 12.The second embodiment is different from the first embodiment inconfigurations of the clutch and the state changing unit.

In the present embodiment, ball bearings 141 and 143 are providedbetween the inner peripheral wall of the fixing flange 11 and the outerperipheral wall of the input shaft 61. Accordingly, the input shaft 61is bearing-supported by the fixing flange 11 via the ball bearings 141and 143.

The housing 12 is fixed to the fixing flange 11 such that a part of anouter wall of the housing 12 is in contact with the wall surface of thefixing flange 11, and an inner peripheral wall of the housing innercylinder portion 121 is in contact with an outer peripheral wall of thefixing flange 11. The housing 12 is fixed to the fixing flange 11 by abolt or the like (not shown). The housing 12 is provided coaxially withthe fixing flange 11 and the input shaft 61.

The arrangement of the motor 20, the speed reducer 30, the ball cam 2,and the like with respect to the housing 12 is the same as that of thefirst embodiment.

In the present embodiment, the output shaft 62 includes the shaftportion 621, the plate portion 622, the cylinder portion 623, and acover 625. The shaft portion 621 is formed in a substantiallycylindrical shape. The plate portion 622 is integrally formed with theshaft portion 621 so as to extend radially outward from one end of theshaft portion 621 in an annular plate shape. The cylinder portion 623 isintegrally formed with the plate portion 622 so as to extend in asubstantially cylindrical shape from an outer edge portion of the plateportion 622 toward a side opposite to the shaft portion 621. The outputshaft 62 is bearing-supported by the input shaft 61 via the ball bearing142. A clutch space 620 is formed inside the cylinder portion 623.

The clutch 70 is provided in the clutch space 620 between the inputshaft 61 and the output shaft 62. The clutch 70 includes a supportportion 73, a friction plate 74, a friction plate 75, and a pressureplate 76. The support portion 73 is formed in a substantiallycircular-annular plate shape so as to extend radially outward from anouter peripheral wall of an end portion of the input shaft 61, on adriven cam 50 side with respect to the plate portion 622 of the outputshaft 62.

The friction plate 74 is formed in a substantially circular-annularplate shape, and is provided on an outer edge portion of the supportportion 73 on a plate portion 622 side of the output shaft 62. Thefriction plate 74 is fixed to the support portion 73. The friction plate74 can come into contact with the plate portion 622 by deforming theouter edge portion of the support portion 73 toward the plate portion622.

The friction plate 75 is formed in a substantially circular-annularplate shape, and is provided on the outer edge portion of the supportportion 73 on a side opposite to the plate portion 622 of the outputshaft 62. The friction plate 75 is fixed to the support portion 73.

The pressure plate 76 is formed in a substantially circular-annularplate shape, and is provided on the driven cam 50 side with respect tothe friction plate 75.

In an engaged state in which the friction plate 74 and the plate portion622 are in contact with each other, that is, engaged with each other, africtional force is generated between the friction plate 74 and theplate portion 622, and relative rotation between the friction plate 74and the plate portion 622 is restricted according to a magnitude of thefrictional force. On the other hand, in a disengaged state in which thefriction plate 74 and the plate portion 622 are separated from eachother, that is, are not engaged with each other, the frictional force isnot generated between the friction plate 74 and the plate portion 622,and the relative rotation between the friction plate 74 and the plateportion 622 is not restricted.

When the clutch 70 is in the engaged state, the torque input to theinput shaft 61 is transmitted to the output shaft 62 via the clutch 70.On the other hand, when the clutch 70 is in the disengaged state, thetorque input to the input shaft 61 is not transmitted to the outputshaft 62.

The cover 625 is formed in a substantially circular-annular shape, andis provided on the cylinder portion 623 of the output shaft 62 so as tocover the pressure plate 76 from a side opposite to the friction plate75.

In the present embodiment, the clutch device 1 includes a state changingunit 90 instead of the state changing unit 80 described in the firstembodiment. The state changing unit 90 includes a diaphragm spring 91 asan “elastic deformation portion”, a return spring 92, a release bearing93, and the like.

The diaphragm spring 91 is formed in a substantially circular-annulardisk spring shape, and is provided on the cover 625 such that one end inthe axial direction, that is, an outer edge portion is in contact withthe pressure plate 76. The diaphragm spring 91 is formed such that theouter edge portion is located on the clutch 70 side with respect to theinner edge portion, and a portion between the inner edge portion and theouter edge portion is supported by the cover 625. The diaphragm spring91 is elastically deformable in the axial direction. Accordingly, thediaphragm spring 91 urges the pressure plate 76 toward the frictionplate 75 by one end in the axial direction, that is, the outer edgeportion. The pressure plate 76 is pressed against the friction plate 75.The friction plate 74 is pressed against the plate portion 622. That is,the clutch 70 is normally in the engaged state.

In the present embodiment, the clutch device 1 is a so-called normallyclosed clutch device that is normally in the engaged state.

The return spring 92 is, for example, a coil spring, and is provided ona side opposite to the driven cam main body 51 with respect to thedriven cam step surface 53 such that one end of the return spring 92 isin contact with the driven cam step surface 53.

The release bearing 93 is provided between the other end of the returnspring 92 and the inner edge portion of the diaphragm spring 91. Thereturn spring 92 urges the release bearing 93 toward the diaphragmspring 91. The release bearing 93 bearing-supports the diaphragm spring91 while receiving a load in a thrust direction from the diaphragmspring 91. An urging force of the return spring 92 is smaller than anurging force of the diaphragm spring 91.

As shown in FIG. 12, when the ball 3 is located at one end of the drivecam groove 400 and the driven cam groove 500, a distance between thedrive cam 40 and the driven cam 50 is relatively small, and a gap Sp2 isformed between the release bearing 93 and the driven cam step surface 53of the driven cam 50. Therefore, the friction plate 74 is pressedagainst the plate portion 622 by the urging force of the diaphragmspring 91, the clutch 70 is in the engaged state, and transmission oftorque between the input shaft 61 and the output shaft 62 is allowed.

When electric power is supplied to the coil 22 of the motor 20 under thecontrol of the ECU 10, the motor 20 rotates, the torque is output fromthe speed reducer 30, and the drive cam 40 rotates relatively withrespect to the housing 12. Accordingly, the ball 3 rolls from one end tothe other end of the drive cam groove 400 and the driven cam groove 500.Therefore, the driven cam 50 moves relatively with respect to thehousing 12 and the drive cam 40 in the axial direction, that is, movestoward the clutch 70. Thus, the gap Sp2 between the release bearing 93and the driven cam step surface 53 of the driven cam 50 is reduced, andthe return spring 92 is compressed in the axial direction between thedriven cam 50 and the release bearing 93.

When the driven cam 50 further moves toward the clutch 70, the returnspring 92 is maximally compressed, and the release bearing 93 is pressedtoward the clutch 70 by the driven cam 50. Accordingly, the releasebearing 93 moves toward the clutch 70 against a reaction force from thediaphragm spring 91 while pressing the inner edge portion of thediaphragm spring 91.

When the release bearing 93 moves toward the clutch 70 while pressingthe inner edge portion of the diaphragm spring 91, the inner edgeportion of the diaphragm spring 91 moves toward the clutch 70, and theouter edge portion of the diaphragm spring 91 moves toward an oppositeside of the clutch 70. Accordingly, the friction plate 74 is separatedfrom the plate portion 622, and the state of the clutch 70 is changedfrom the engaged state to the disengaged state. As a result,transmission of torque between the input shaft 61 and the output shaft62 is interrupted.

When the clutch transmission torque is zero, the ECU 10 stops therotation of the motor 20. Accordingly, the state of the clutch 70 ismaintained in the disengaged state. As described above, the diaphragmspring 91 of the state changing unit 90 receives a force in the axialdirection from the driven cam 50, and can change the state of the clutch70 to the engaged state or the disengaged state according to a relativeposition of the driven cam 50 in the axial direction with respect to thedrive cam 40.

In the present embodiment, the inner sealing member 401 and the outersealing member 402 as the “sealing members” can also maintain anairtight or liquid-tight state between the accommodation space 120 andthe clutch space 620.

In the present embodiment, the clutch device 1 does not include the oilsupply portion described in the first embodiment. That is, in thepresent embodiment, the clutch 70 is a dry clutch.

As described above, the present disclosure is also applicable to anormally closed clutch device including the dry clutch.

As described above, in the present embodiment, the state changing unit90 includes the diaphragm spring 91 as the “elastic deformation portion”that is elastically deformable in the axial direction of the driven cam50 as the “translation portion”.

By controlling the rotation angle position of the motor 20, thrustcontrol of the clutch 70 can be performed with high accuracy based onthe displacement and load characteristics of the diaphragm spring 91.Therefore, the variation in the load acting on the clutch 70 withrespect to the variation in the stroke of the driven cam 50 can bereduced. Accordingly, as in the first embodiment, the load control canbe performed with high accuracy, and the clutch device 1 can becontrolled with high accuracy.

Third Embodiment

A part of a clutch device according to a third embodiment is shown inFIG. 13. The third embodiment is different from the first embodiment ina configuration of the sun gear 31 and the like.

In the present embodiment, the sun gear 31 is formed separately from therotor 23 and is formed of a material having a specific gravity smallerthan that of the rotor 23. More specifically, the sun gear 31 is formedof, for example, a resin. A specific gravity of the resin is smallerthan that of pure iron forming the rotor 23.

As described above, in the present embodiment, the sun gear 31 is formedseparately from the rotor 23 and is formed of a material having aspecific gravity smaller than that of the rotor 23.

Therefore, an inertia moment around the sun gear 31 serving as the“input shaft” can be further reduced, and higher response can beachieved. The cost can be reduced and rattle noise can be lowered.

In the present embodiment, a 3k-type strange planetary gear speedreducer is employed, and the torque applied to the sun gear 31 is small,so that even if the sun gear 31 is formed of a material having a smallspecific gravity, there is no problem in strength.

Fourth Embodiment

A part of a clutch device according to a fourth embodiment is shown inFIG. 14. The fourth embodiment is different from the first embodiment inthe configuration of the sealing member.

In the present embodiment, the “sealing member” includes the innersealing member 401 (not shown in FIG. 14) and an outer sealing member404. Similarly to the inner sealing member 401, the outer sealing member404 is formed in an annular shape using an elastic material such asrubber. More specifically, the outer sealing member 404 includes a sealannular portion 940, a first outer lip portion 941, a second outer lipportion 942, a first inner lip portion 943, and a second inner lipportion 944. The seal annular portion 940, the first outer lip portion941, the second outer lip portion 942, the first inner lip portion 943,and the second inner lip portion 944 are integrally formed.

The seal annular portion 940 is formed in a substantiallycircular-annular shape. The first outer lip portion 941 is formed in anannular shape over the entire range in the circumferential direction ofthe seal annular portion 940 so as to extend from the seal annularportion 940 to be inclined radially outward and toward one side in theaxial direction. The second outer lip portion 942 is formed in anannular shape over the entire range in the circumferential direction ofthe seal annular portion 940 so as to extend from the seal annularportion 940 to be inclined radially outward and toward the other side inthe axial direction. The first inner lip portion 943 is formed in anannular shape over the entire range in the circumferential direction ofthe seal annular portion 940 so as to extend from the seal annularportion 940 to be inclined radially inward and toward one side in theaxial direction. The second inner lip portion 944 is formed in anannular shape over the entire range in the circumferential direction ofthe seal annular portion 940 so as to extend from the seal annularportion 940 to be inclined radially inward and toward the other side inthe axial direction. Accordingly, the outer sealing member 404 is formedto have an X-shape in a cross section taken along a virtual planeincluding all the axes (see FIG. 14).

As shown in FIG. 14, the outer sealing member 404 is provided in anannular seal groove portion 441 formed in the outer peripheral wall ofthe drive cam outer cylinder portion 44. Tip portions of the first innerlip portion 943 and the second inner lip portion 944 are in contact withthe seal groove portion 441. That is, the outer sealing member 404 isprovided so as to be in contact with the drive cam 40 on the radiallyouter side of the drive cam 40 as the “rotation portion”.

Tip portions of the first outer lip portion 941 and the second outer lipportion 942 are in contact with the inner peripheral wall of the fixingcylinder portion 131 of the fixing portion 130. Therefore, a contactarea between the outer sealing member 404 and the fixing portion 130 issmaller than a contact area between the outer sealing member 402 and thefixing portion 130 in the first embodiment. Accordingly, a slidingresistance acting on the outer sealing member 404 during the rotation ofthe drive cam 40 can be reduced.

The first outer lip portion 941 and the second outer lip portion 942 ofthe outer sealing member 404 seal the drive cam outer cylinder portion44 and the inner peripheral wall of the fixing cylinder portion 131 inan airtight or liquid-tight manner while being elastically deformed inthe radial direction. The outer sealing member 404 is a so-called lipseal.

The present embodiment has the same configuration as that of the firstembodiment except for the above-described points.

As described above, in the present embodiment, the outer sealing member404 as the “sealing member” is a lip seal.

Therefore, the contact area between the outer sealing member 404 and thefixing portion 130 can be reduced. Accordingly, a sliding resistanceacting on the outer sealing member 404 during the rotation of the drivecam 40 can be reduced. Therefore, a decrease in efficiency duringoperation of the clutch device 1 can be reduced.

Fifth Embodiment

A part of a clutch device according to a fifth embodiment is shown inFIG. 15. The fifth embodiment is different from the first embodiment inthe configuration of the sealing member.

In the present embodiment, the “sealing member” includes the innersealing member 401 (not shown in FIG. 15) and an outer sealing member405. The outer sealing member 405 includes a seal main body 95 and ametal ring 96. The seal main body 95 is formed in an annular shape usingan elastic material such as rubber. The metal ring 96 is formed of metalin an annular shape.

More specifically, the seal main body 95 includes a seal inner cylinderportion 951, a seal plate portion 952, a seal outer cylinder portion953, and a seal lip portion 954. The seal inner cylinder portion 951,the seal plate portion 952, the seal outer cylinder portion 953, and theseal lip portion 954 are integrally formed.

The seal inner cylinder portion 951 is formed in a substantiallycylindrical shape. The seal plate portion 952 is formed in an annularplate shape so as to extend radially outward from one end portion of theseal inner cylinder portion 951. The seal outer cylinder portion 953 isformed in a substantially cylindrical shape so as to extend from anouter edge portion of the seal plate portion 952 to the same side as theseal inner cylinder portion 951. An end portion of the seal outercylinder portion 953 opposite to the seal plate portion 952 is locatedcloser to the seal plate portion 952 than an end portion of the sealinner cylinder portion 951 opposite to the seal plate portion 952. Theseal lip portion 954 is formed in an annular shape so as to protruderadially outward from the end portion of the seal outer cylinder portion953 opposite to the seal plate portion 952. The seal lip portion 954 isformed such that a shape of a tip portion thereof, which is an outeredge portion thereof, is substantially a right angle in a cross sectiontaken along a virtual plane including the all the axes (see FIG. 15).

The metal ring 96 includes a metal cylinder portion 961 and a metalplate portion 962. The metal cylinder portion 961 and the metal plateportion 962 are integrally formed.

The metal cylinder portion 961 is formed in a substantially cylindricalshape. The metal plate portion 962 is formed in an annular plate shapeso as to extend radially outward from one end portion of the metalcylinder portion 961. Accordingly, the metal ring 96 is formed to havean L shape in a cross section taken along a virtual plane including allthe axes (see FIG. 15).

The metal ring 96 is integrally formed with the seal main body 95 suchthat an inner peripheral wall of the metal cylinder portion 961 is incontact with an outer peripheral wall of the seal inner cylinder portion951, and a surface of the metal plate portion 962 opposite to the metalcylinder portion 961 is in contact with a surface of the seal plateportion 952 on a seal inner cylinder portion 951 side. The “integrallyformed” means, for example, integrally forming multiple members byinsert molding or the like (the same applies hereinafter).

As shown in FIG. 15, the outer sealing member 405 is provided in anannular seal groove portion 431 formed in an outer peripheral wall ofthe drive cam plate portion 43. The seal groove portion 431 is formed soas to extend toward the drive cam outer cylinder portion 44 from an endsurface of the drive cam plate portion 43 opposite to the drive camouter cylinder portion 44.

In the outer sealing member 405, an inner peripheral wall of the sealinner cylinder portion 951 is in contact with the seal groove portion431. That is, the outer sealing member 405 is provided so as to be incontact with the drive cam 40 on the radially outer side of the drivecam 40 as the “rotation portion”.

A tip portion of the seal lip portion 954, which is an outer edgeportion of the seal lip portion 954, is in contact with the innerperipheral wall of the fixing cylinder portion 131 of the fixing portion130. Therefore, a contact area between the outer sealing member 405 andthe fixing portion 130 is significantly reduced as compared with acontact area between the outer sealing member 402 and the fixing portion130 in the first embodiment. Accordingly, a sliding resistance acting onthe outer sealing member 405 during rotation of the drive cam 40 can besignificantly reduced.

The seal lip portion 954 of the outer sealing member 405 seals the drivecam plate portion 43 and the inner peripheral wall of the fixingcylinder portion 131 in an airtight or liquid-tight manner while beingelastically deformed in the radial direction. The outer sealing member405 is a so-called oil seal.

The metal ring 96 stabilizes a shape of the outer sealing member 405, inparticular, a shape of the seal inner cylinder portion 951 and the sealplate portion 952. Since the seal lip portion 954 is formed at the endportion of the seal outer cylinder portion 953 opposite to the sealplate portion 952, the tip portion of the seal lip portion 954 canflexibly follow the inner peripheral wall of the fixing cylinder portion131 by elastically deforming the end portion of the seal outer cylinderportion 953 in the radial direction.

The present embodiment has the same configuration as that of the firstembodiment except for the above-described points.

As described above, in the present embodiment, the outer sealing member405 as the “sealing member” is an oil seal.

Therefore, the contact area between the outer sealing member 405 and thefixing portion 130 can be reduced. Accordingly, the sliding resistanceacting on the outer sealing member 405 during the rotation of the drivecam 40 can be reduced. Therefore, a decrease in efficiency duringoperation of the clutch device 1 can be reduced.

Other Embodiments

In the above-described embodiments, the meshing length L2 between thesun gear 31 and the planetary gear 32 is set to about 50% of the gearwidth L1 of the planetary gear 32. On the other hand, in anotherembodiment, the meshing length L2 between the sun gear 31 and theplanetary gear 32 may be set to any length with respect to the gearwidth L1 of the planetary gear 32 as long as the meshing length L2 issmaller than the gear width L1 of the planetary gear 32.

In the above-described third embodiment, the sun gear 31 is formed of aresin, which is a material having a specific gravity smaller than thatof the rotor 23. On the other hand, in another embodiment, the sun gear31 may be formed of, for example, aluminum, which is a material having aspecific gravity smaller than that of the rotor 23.

In another embodiment, the rotor 23 and the sun gear 31 may beintegrally formed of the same material.

In another embodiment, the motor 20 may not include the magnet 230 asthe “permanent magnet”.

In another embodiment, the drive cam 40 as the “rotation portion” may beformed separately from the second ring gear 35 of the speed reducer 30.

In another embodiment, the drive cam 40 as the “rotation portion” may beformed such that the inner edge portion and the outer edge portion areat the same position in the axial direction.

In another embodiment, the sealing member for maintaining an airtight orliquid-tight state between the accommodation space and the clutch spacemay not be provided.

In the above-described embodiments, the inner rotor type motor 20 inwhich the rotor 23 is provided on the radially inner side of the stator21 has been described. However, in another embodiment, the motor 20 maybe an outer rotor type motor in which the rotor 23 is provided on theradially outer side of the stator 21.

In the above-described embodiments, an example has been shown in whichthe rotational translation unit is a rolling body cam including a drivecam, a driven cam, and a rolling element. On the other hand, in anotherembodiment, the rotational translation unit may be configured by, forexample, a “slide screw” or a “ball screw” as long as the rotationaltranslation portion includes a rotation portion that rotates relativelywith respect to the housing and a translation portion that moves withrespect to the housing in the axial direction when the rotation portionrotates with respect to the housing.

In another embodiment, an elastic deformation portion of the statechanging unit may be, for example, a coil spring, rubber, or the like aslong as the elastic deformation portion is elastically deformable in theaxial direction. In another embodiment, the state changing unit may notinclude the elastic deformation portion, and may be configured only by arigid body.

In another embodiment, the number of the drive cam grooves 400 and thenumber of the driven cam grooves 500 are not limited to five and anynumber of grooves may be formed as long as the number of the drive camgrooves 400 and the number of the driven cam grooves 500 are three ormore. Any number of balls 3 may be provided according to the number ofthe drive cam grooves 400 and the driven cam grooves 500.

The present disclosure is not limited to a vehicle that travels by drivetorque from an internal combustion engine, and can be applied to anelectric vehicle, a hybrid vehicle, or the like that can travel by drivetorque from a motor.

In another embodiment, the torque may be input from the secondtransmission portion, and output from the first transmission portion viathe clutch. For example, when one of the first transmission portion andthe second transmission portion is non-rotatably fixed, the rotation ofthe other of the first transmission portion and the second transmissionportion can be stopped by engaging the clutch. In this case, the clutchdevice can be used as a brake device.

As described above, the present disclosure is not limited to theabove-described embodiments and can be implemented in a variety ofembodiments without departing from the scope of the subject matter.

While the present disclosure has been described with reference toembodiments thereof, it is to be understood that the disclosure is notlimited to the embodiments and constructions. To the contrary, thepresent disclosure is intended to cover various modification andequivalent arrangements. In addition, while the various elements areshown in various combinations and configurations, which are exemplary,other combinations and configurations, including more, less or only asingle element, are also within the spirit and scope of the presentdisclosure.

What is claimed is:
 1. A clutch device comprising: a housing; a primemover including a stator fixed to the housing, and a rotor rotatablerelative to the stator, the prime mover being capable of outputtingtorque from the rotor by supply of electric power to the prime mover; aspeed reducer configured to reduce torque of the prime mover and outputthe reduced torque; a rotational translation unit including a rotationportion that rotates relative to the housing upon receiving an input ofthe torque output from the speed reducer, and a translation portion thatmoves relative to the housing in an axial direction in accordance withrotation of the rotation portion relative to the housing; a clutchprovided between a first transmission portion and a second transmissionportion that are rotatable relative to the housing, the clutch beingconfigured to allow transmission of torque between the firsttransmission portion and the second transmission portion in an engagedstate of the clutch, and interrupt the transmission of torque betweenthe first transmission portion and the second transmission portion in adisengaged state of the clutch; and a state changing unit configured toreceive a force along the axial direction from the translation portionand change a state of the clutch to the engaged state or the disengagedstate according to a position of the translation portion in the axialdirection relative to the housing, wherein the speed reducer includes asun gear rotatable integrally together with the rotor, and a planetarygear configured to revolve in a circumferential direction of the sungear while rotating in a state of meshing with the sun gear, and a gearwidth of the sun gear is set such that a length in the axial directionby which the sun gear and the planetary gear are overlapped is smallerthan a gear width of the planetary gear, wherein the sun gear and theplanetary gear are configured such that C−L2·tan α≥0 and L1>L2, where Cis a backlash in a circumferential direction on a meshing pitch circlebetween the sun gear and the planetary gear when an inclination angle ofthe planetary gear with respect to the sun gear is 0, α is aninclination angle of the planetary gear with respect to the sun gear, L1is the gear width of the planetary gear, and L2 is the meshing lengthbetween the sun gear and the planetary gear.
 2. The clutch deviceaccording to claim 1, wherein the length by which the sun gear and theplanetary gear are overlapped is set within a range from 20% to 50% ofthe gear width of the planetary gear in length.
 3. The clutch deviceaccording to claim 1, wherein the sun gear is formed separately from therotor and is formed of a material having a specific gravity smaller thana specific gravity of the rotor.
 4. The clutch device according to claim1, wherein the prime mover includes a permanent magnet provided in therotor.
 5. The clutch device according to claim 1, wherein the speedreducer includes an annular carrier rotatably supporting the planetarygear and being rotatable relative to the sun gear, a first ring gearcapable of meshing with the planetary gear, and a second ring gearcapable of meshing with the planetary gear and outputting the torque tothe rotational translation unit, the second ring gear being differentfrom the first ring gear in number of teeth of a tooth portion.
 6. Theclutch device according to claim 5, wherein the first ring gear is fixedto the housing, and the second ring gear is integrally rotatable withthe rotation portion.
 7. The clutch device according to claim 5, whereinthe rotation portion is formed integrally with the second ring gear. 8.The clutch device according to claim 1, wherein the rotation portion isa drive cam having drive cam grooves formed on one surface of therotation portion, the translation portion is a driven cam having drivencam grooves formed on one surface of the translation portion, and therotational translation unit is a rolling body cam including the drivecam, the driven cam and rolling bodies, the rolling bodies beingrollable between the drive cam grooves and the driven cam grooves. 9.The clutch device according to claim 1, wherein the rotation portionhaving an inner edge portion and an outer edge portion that are locatedat different positions in the axial direction.
 10. The clutch deviceaccording to claim 1, wherein the prime mover and the speed reducer areprovided in an accommodation space formed inside the housing, therotation portion being positioned between the accommodation space andthe clutch, the clutch is provided in a clutch space, the rotationportion being positioned between the accommodation space and the clutchspace, and the clutch device further comprises an annular sealing memberbeing in contact with the rotation portion and maintaining an air-tightor liquid-tight state between the accommodation space and the clutchspace.
 11. The clutch device according to claim 10, wherein the sealingmember is an O-ring, a lip seal, or an oil seal.
 12. The clutch deviceaccording to claim 1, wherein the state changing unit includes anelastic deformation portion that is elastically deformable in the axialdirection of the translation portion.
 13. A clutch device comprising: ahousing; a prime mover including a stator fixed to the housing, and arotor rotatable relative to the stator, the prime mover being capable ofoutputting torque from the rotor by supply of electric power to theprime mover; a speed reducer configured to reduce torque of the primemover and output the reduced torque; a rotational translation unitincluding a rotation portion that rotates relative to the housing uponreceiving an input of the torque output from the speed reducer, and atranslation portion that moves relative to the housing in an axialdirection in accordance with rotation of the rotation portion relativeto the housing; a clutch provided between a first transmission portionand a second transmission portion that are rotatable relative to thehousing, the clutch being configured to allow transmission of torquebetween the first transmission portion and the second transmissionportion in an engaged state of the clutch, and interrupt thetransmission of torque between the first transmission portion and thesecond transmission portion in a disengaged state of the clutch; and astate changing unit configured to receive a force along the axialdirection from the translation portion and change a state of the clutchto the engaged state or the disengaged state according to a position ofthe translation portion in the axial direction relative to the housing,wherein the speed reducer includes a sun gear rotatable integrallytogether with the rotor, and a planetary gear configured to revolve in acircumferential direction of the sun gear while rotating in a state ofmeshing with the sun gear, and a gear width of the sun gear is set suchthat a length in the axial direction by which the sun gear and theplanetary gear are overlapped is smaller than a gear width of theplanetary gear, wherein the sun gear is formed separately from the rotorand is formed of a material having a specific gravity smaller than aspecific gravity of the rotor.
 14. A clutch device comprising: ahousing; a prime mover including a stator fixed to the housing, and arotor rotatable relative to the stator, the prime mover being capable ofoutputting torque from the rotor by supply of electric power to theprime mover; a speed reducer configured to reduce torque of the primemover and output the reduced torque; a rotational translation unitincluding a rotation portion that rotates relative to the housing uponreceiving an input of the torque output from the speed reducer, and atranslation portion that moves relative to the housing in an axialdirection in accordance with rotation of the rotation portion relativeto the housing; a clutch provided between a first transmission portionand a second transmission portion that are rotatable relative to thehousing, the clutch being configured to allow transmission of torquebetween the first transmission portion and the second transmissionportion in an engaged state of the clutch, and interrupt thetransmission of torque between the first transmission portion and thesecond transmission portion in a disengaged state of the clutch; and astate changing unit configured to receive a force along the axialdirection from the translation portion and change a state of the clutchto the engaged state or the disengaged state according to a position ofthe translation portion in the axial direction relative to the housing,wherein the speed reducer includes a sun gear rotatable integrallytogether with the rotor, and a planetary gear configured to revolve in acircumferential direction of the sun gear while rotating in a state ofmeshing with the sun gear, and a gear width of the sun gear is set suchthat a length in the axial direction by which the sun gear and theplanetary gear are overlapped is smaller than a gear width of theplanetary gear, wherein the rotation portion having an inner edgeportion and an outer edge portion that are located at differentpositions in the axial direction.
 15. A clutch device comprising: ahousing; a prime mover including a stator fixed to the housing, and arotor rotatable relative to the stator, the prime mover being capable ofoutputting torque from the rotor by supply of electric power to theprime mover; a speed reducer configured to reduce torque of the primemover and output the reduced torque; a rotational translation unitincluding a rotation portion that rotates relative to the housing uponreceiving an input of the torque output from the speed reducer, and atranslation portion that moves relative to the housing in an axialdirection in accordance with rotation of the rotation portion relativeto the housing; a clutch provided between a first transmission portionand a second transmission portion that are rotatable relative to thehousing, the clutch being configured to allow transmission of torquebetween the first transmission portion and the second transmissionportion in an engaged state of the clutch, and interrupt thetransmission of torque between the first transmission portion and thesecond transmission portion in a disengaged state of the clutch; and astate changing unit configured to receive a force along the axialdirection from the translation portion and change a state of the clutchto the engaged state or the disengaged state according to a position ofthe translation portion in the axial direction relative to the housing,wherein the speed reducer includes a sun gear rotatable integrallytogether with the rotor, and a planetary gear configured to revolve in acircumferential direction of the sun gear while rotating in a state ofmeshing with the sun gear, and a gear width of the sun gear is set suchthat a length in the axial direction by which the sun gear and theplanetary gear are overlapped is smaller than a gear width of theplanetary gear, wherein the prime mover and the speed reducer areprovided in an accommodation space formed inside the housing, therotation portion being positioned between the accommodation space andthe clutch, the clutch is provided in a clutch space, the rotationportion being positioned between the accommodation space and the clutchspace, and the clutch device further comprises an annular sealing memberbeing in contact with the rotation portion and maintaining an air-tightor liquid-tight state between the accommodation space and the clutchspace.